The present invention relates to a display device having a display unit which displays map information for use in a navigation system for a vehicle.
Recently, a navigation system has been studied and developed for a vehicle for leading the vehicle to a predetermined destination. The system has a display unit displaying map information prestored in and read from a memory, together with a place pointed out on the map where the vehicle is at present.
In such a navigation system, the display unit is located in the passenger compartment of the vehicle. Therefore, whether the information displayed on the display unit is clear to observe or not depends on the ambient light level in the passenger compartment. That is, in the daytime, the image on the display unit should be brightened to make it clearly observable since the ambient light level is often quite high. On the other hand, at night, if the color on the display unit is the same as that displayed in the daytime, eye fatigue may result since the display may be excessively bright for nighttime conditions.
In order to eliminate the above problem, in a conventional display device, the brightness of the display unit is decreased at night by a dimmer or the like. However, the conventional device is disadvantageous in that the information displayed on the display unit is sometimes indistinct.